Around 1,000 headteachers are due to march on Downing Street in an unprecedented protest over funding.
Organisers of the grassroots protest say school leaders from across England also will deliver a petition to Number 10.
It is the first time school leaders have staged a demonstration in this way, campaigners say.
It comes after figures reveal that the number of secondary schools in England running at a loss had nearly trebled in four years.
The National Association of Head Teachers (NAHT) said government figures show that £2.8bn has been cut from schools budgets in the last three years.
The Department for Education (DfE) says schools have never been so well-funded and a funding formula, due to be introduced in 2020, would ensure a more level playing field for smaller, cash-strapped schools.
But headteachers say that is at odds with figures from the Institute for Fiscal Studies which show that funding per pupil fell by 8% between 2010 and 2018.
Compared to last year, England's schools have 137,000 more pupils but 5,400 fewer teachers, and 2,800 fewer teaching assistants, according to the Office for National Statistics.
Sky News has spent a week looking at the issue inside schools as part of a special report into education funding.
Judy Shaw, vice-president of the NAHT, says some schools are "on the brink of collapse".
"We just haven't got the money to pay for things anymore. In the past, if we needed extra support for special educational needs or a speech therapist or behavioural psychologist then that was funded centrally via the local authority. Now we have to find money from our own budgets – and the money simply isn't there any more.
"So when the government says we have never been so well-funded, what they're not telling you is that we're paying out for more things than ever before."
Mrs Shaw, a headteacher at Tuel Lane Infant's School in Sowerby Bridge, Yorkshire, said at its worse she was left with just £80 in the school's budget at the end of the academic year.
"The school was built in 1879 and it's a huge old Victorian building not built for 21st century education. We struggle to keep it repaired and it costs us and arm and a leg to keep it maintained.
"If a tile drops off the roof tomorrow, we'll struggle to find the money to fix it. It's that bad."
She said funds for repairs and maintenance had dropped from £25,000 a year to £5,000, adding that the budget was at "breaking point".
One day last year at Riverside Junior School in Hebden Bridge, just a few miles down the road, a lump of concrete fell from a ceiling narrowly missing a teacher sitting at her desk.
Headteacher Rachel Burton said she spends more time patching up the school than running it.
"Budgets are tight, really tight. Just the other day I had a child turn up on the doorstep of the school. That child has very specific special educational needs and I have to find the money to pay for a support teacher to come in. It's expensive. We do it, obviously.
"When bits of the school start falling off, it's a toss up between fixing the roof and helping to support a child.
"The government need to wake up to the reality. We cannot teach like this.
"When I became a head I always expected to manage budgets, what I didn't expect to be doing was propping up roofs and knocking off rotten plaster with my site manager."
In a survey of school leaders more than a fifth said their budget for 2017/18 was in deficit – an increase of 13% since 2015, according to the NAHT.
In response, the government said it was spending record amounts on schools.
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A DfE spokeswoman said: "There is more money going into schools than ever before, rising to a record #43.5 billion by 2020 – 50% more in real terms per pupil than in 2000.
"Every school attracts more funding per pupil through the National Funding Formula, high needs funding has risen to over £6bn this year, and the 3.5% pay rise we announced for classroom teachers on the main pay range is backed by £508m government funding."
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